In recent years, new fine processing techniques have been developed along with high integration and high performance of LSI. A chemical mechanical polishing (hereinafter, also abbreviated as “CMP”) method is one of the methods, and is a technique frequently used in an LSI production process, in particular, in a multilayer wiring forming process.
One of the cases in which this CMP method is applied is polishing of an object to be polished containing a phase change alloy. The phase change alloy is an alloy being one of the phase change materials that reversibly change the phase between an amorphous phase and a crystal phase, and typically includes a germanium-antimony-tellurium alloy (GST alloy), indium antimonide (InSb), and the like. These phase change alloys are used as a structural material of a phase change device such as a phase change random access memory (PCRAM or PCRAM), utilizing the characteristics of the phase change material.
Herein, the phase change alloy greatly differs from other metal materials in the physical properties of being softer and the like as compared with the other metal materials such as copper, and tungsten. Therefore, even when the polishing composition that is used in a conventional CMP method is used as it is in the polishing of a phase change alloy, a satisfactory result may not be obtained. In particular, a practically sufficient polishing rate is difficult to be obtained.
Conventionally, as a technique to improve the polishing rate in the polishing of a phase change alloy, there is a technique described in Patent Literature 1. In Patent Literature 1, into a slurry composition for CMP for a phase change memory device, deionized water and a nitrogen compound such as triethylamine are contained, so that the improvement in the polishing rate to a phase change material layer composed of a GST alloy and the like is attained.
As one of the other cases in which the CMP method is applied, there is a process of forming a wiring structure in an insulator layer. In the process of forming a wiring structure using a CMP method, first, a metal layer composed of tungsten and the like is formed on an insulator layer (for example, a SiO2 layer) on which a recess is formed, so that at least the recess is completely buried. Next, the metal layer is polished and removed by the CMP method until the insulator layer is exposed except for the part of the recess, so that a wiring part is formed in the recess.
Conventionally, as a technique to improve the polishing rate in the polishing of a metal layer, there is a technique described in Patent Literature 2. In Patent Literature 2, a catalyst having multiple oxidation states (for example, ferric nitrate and the like) is used, so that the improvement in the polishing rate to a metal layer is attained.